An inverter in accordance with the conventional technology, which is provided with connections limiting the current-increase rate (di/dt) and the voltage-increase rate (du/dt), is illustrated with respect to one phase in FIG. 1. Therein, U.sub.DC is the supplying DC-voltage, C.sub.DC is the filter capacitor of the DC-voltage, S.sub.1 and S.sub.2 are semiconductor switches, D.sub.1 and D.sub.2 are so-called zero diodes, L is the choke limiting the rate of increase of the current, whereas the diode D.sub.5 and the resistor R.sub.3 constitute an alternative route for the current of the choke, and C.sub.1 and C.sub.2 are the capacitors limiting the rate of increase of the voltage, whereat diodes D.sub.3 and D.sub.4 as well as resistors R.sub.1 and R.sub.2, together with C.sub.1 and C.sub.2, form so-called polarized RC-shields.
The arrangement of FIG. 1 constitutes a change-over switch by which the poles of the input voltage can be alternately connected to the output pole. The change-over of the switch, e.g., from the lower branch to the upper branch takes place by opening S.sub.2, which had been conductive, and by closing S.sub.1. Thus, C.sub.1, which had been charged to a voltage U.sub.DC, is discharged through the resistor R.sub.1. C.sub.2, whose voltage has been zero, is charged along the path U.sub.DC -L-S.sub.1 -D.sub.4 -C.sub.2. After C.sub.2 has been charged, excess current of the choke L is turned so as to pass vid D.sub.5 and R.sub.3, being gradually reduced to zero, at which time a stable condition has been reached. The change-over of the switch in the opposite direction takes place in a corresponding way.
The operation of the inverter in accordance with FIG. 1, however, involves the drawback that the energy 1/2CU.sup.2 of the capacitor protecting with respect to the voltage increase rate, discharged on each change-over of the switch, as well as the energy 1/2LI.sup.2 .sub.max charged in the choke protecting with respect to the current increase rate on swinging of the resonance circuit are converted to heat in the resistors R.sub.1, R.sub.2 and R.sub.3. The power loss is proportional to the number of change-overs of the switches per unit of time, which makes the efficiency of the inverter poor at high (higher than 1 kHz) frequencies.